1. Field of the Invention
The present invention relates to an apparatus to drive an objective lens of an optical pickup, and more particularly, to an apparatus to drive an objective lens of an optical pickup to actively control tilt between the optical pickup and the recording surface of a disk.
2. Description of the Related Art
Disk drives record and read information on and from a disk as a recording medium by irradiating a laser beam onto the disk. Generally, a disk drive includes a turntable on which a disk is mounted, a spindle motor to rotate the turntable, and an optical pickup to irradiate a laser beam onto the recording surface of the disk to record and/or reproduce information on/from the disk.
Here, in order to form a precisely focused optical spot, a laser beam output from an optical pickup has to be orthogonal to the recording surface of a disk. If the laser beam deviates from the orthogonal direction, a precise optical spot cannot be formed on the disk so that errors occur in recording and/or reproducing data on/from the disk. Accordingly, in order to precisely form an optical spot on a selected track of a disk, a laser beam has to be orthogonal to the recording surface of the disk. Here, a process of adjusting a laser beam to be orthogonal to the recording surface of a disk is referred to as a tilt adjustment or a skew adjustment. In general, an optical pickup includes an apparatus to drive an objective lens to control the location of the objective lens in a focus direction and a tracking direction, so as to focus a laser beam on a selected track of the recording surface of a disk. However, although such an apparatus controls a distance between the objective lens and the recording surface of the disk so that the focus of an optical spot is maintained and the optical spot traces a selected track, the apparatus cannot directly control the recording surface of the disk and the incident angle of the laser beam. Accordingly, a tilt adjustment mechanism has been required to more precisely record and/or reproduce information.
A conventional apparatus to drive an objective lens of an optical pickup having an active tilt adjustment mechanism as illustrated in FIGS. 1 and 2, has been provided. An optical pickup includes an apparatus to drive an objective lens, and has a focus and tracking adjustment mechanism to drive a blade 2 on which an objective lens 1 is mounted in a focus direction A and a tracking direction B, and a tilt adjustment mechanism to drive the blade 2 in a tilt direction C.
Here, the focus and tracking adjustment mechanism has a general structure including a focus coil 3, tracking coils 4, and a magnet 8. Consequently, currents flowing through the focus coil 3 and the tracking coils 4 are controlled to generate an electromagnetic force to drive the blade 2 in a corresponding direction. Reference numeral 5 denotes wires that support and allow the blade 2 to move toward a holder 6.
The tilt adjustment mechanism is formed of iron cores 17a and 17b inserted into bosses 16a and 16b on a base 10, tilt coils 15a and 15b winding around the bosses 16a and 16b, and tilt magnets 14a and 14b installed on the blade 2 to be opposite to the iron cores 17a and 17b. Therefore, the iron cores 17a and 17b are magnetized according to the direction of the currents flowing through the tilt coils 15a and 15b. Thereafter, a magnetic field between the magnetized iron cores 17a and 17b and the tilt magnets 14a and 14b drives the blade 2 in the tilt direction C.
In such an arrangement, since the tilt adjustment mechanism has to be installed in addition to the focus and tracking adjustment mechanism, the number of components increases. In addition, since the tilt magnets 14a and 14b are installed on the blade 2 as a driving portion, the weight of the driving portion increases so that the response speed or the driving portion is deteriorated.
As a result, a new structure of actively adjusting a tilt between a disk and an optical pickup by using a simple configuration is required.